There are known various types of pushbutton devices used in the operating portion of various sorts of electronic devices or the like, in one of which a plurality of buttons are coupled with a base plate by flexible arms respectively. Each button is provided with a drive member at the rear side thereof to drive a push switch.
Such components of the device, namely the buttons, the arms and the drive members are usually formed integrally by molding, which is easy and may reduce the producing cost.
However such unitary structure pushbutton devices of the prior art have only a single stage button array, which limits design of the device and makes it very hard to increase the number of button in the limited space available.
Then the inventors of the present invention provided the idea of the multistage button device shown in FIG. 11, where first buttons 101 are provided on a base 100 in a row across the width of the device. Above the row of the first buttons 101, a second row of second buttons 102 are arranged in the same manner. Each first button 101, is integrally connected with the base 100 by an elastic first arm 103. The second buttons 102 are connected with the base 100 behind the first buttons 101 by elastic second arms 104 which are located between adjacent first buttons 101 as shown in the front view of FIG. 11.
The device of FIG. 11 is produced by using two molds as shown in FIG. 12. A first mold 105 has cavities 107 for molding the front part of the second buttons 102, cavities 108 for molding the front portions of the first arms 103 and a cavity 109 for the front part of the base 100. Another second mold 106 has cavities 110 for molding the rear parts of the second buttons 102, cavities 111 for molding the rear portions of the first buttons 101 and the second buttons 102 and a cavity 112 corresponding to the rear part of the base 100.
The first mold 105 and the second mold 106 are so arranged as to be capable of reciprocating movement. The space formed by the first mold 105 and the second mold 106 in the closed position is then filled with the material of the device and the heat and press treatment follow. Then the multistage button device is produced by separating the first mold 105 and the second mold 106.
Such device produced in said manner can provide a multistage button array integrally formed on the single base plate, which may double the number of buttons and arrange a lot of buttons in a limited space without increasing the number of parts and assembling process.
However the device cannot include two parts which will overlap each other in front and rear thereof on the base plate, since the device is produced by separating two molds (i.e., the first and second molds 105, 106) in the back and forth direction. So the second arm 104 cannot be arranged behind the first button 101 or the first arm 103 but must be arranged between adjacent first buttons 101 (as shown in the front view of FIG. 11). Thus the space corresponding to the width of the second arm 104 must be located between adjacent first buttons 101, which limits the density of the button arrangement.